Radiology workers are regularly exposed to low doses of radiation when they obtain patient imagery such as X-rays. While protective gear largely keeps workers within a safe range of radiation exposure, absorbing a little bit is still inevitable. Radiation doses creeping above regulated guidelines pose risk for developing conditions such as cancer, cataracts, skin irritation, or thyroid disease.
Currently, radiology workers are required to wear badges, called dosimeters, on various parts of their bodies for monitoring their radiation exposure. The badges are worn for a month or two and are then sent to the company that made them. It takes weeks for the company to read the data and send a report back to the hospital.
Researchers have engineered yeast “microbreweries” within disposable badges made of freezer paper, aluminum, and tape. Simply adding a drop of water activates the yeast to show radiation exposure as read by an electronic device. On a commercial level, the readout device could one day be a tablet or phone. The badge could also be adapted in the future for nuclear power plant workers and victims of nuclear disasters. The badge would be worn in the lab and recycled after exposure is checked by plugging it into a device.
The success of the badge lies in the quick and measurable response of yeast to radiation — the higher the radiation dose, the higher the percentage of yeast cells that die. Wetting the badge activates the cells that are still alive to eat glucose and release carbon dioxide — the same fermentation process responsible for brewing beer and making bread rise. When carbon dioxide bubbles at the surface, ions also form. The concentration of these ions increases the electrical conductivity of yeast, which can be measured by hooking up the badge to a readout system.
The change in electrical properties of the yeast tells how much radiation damage it incurred. A slow decrease in electrical conductivity over time indicates more damage. Numbers from the readout system translate to rads — the units used by entities like the Occupational Safety and Health Administration (OSHA) to specify limits on how much radiation human tissue can safely absorb. Skin of the whole body, for example, shouldn't be exposed to more than 7.5 rad over a three-month period.
The new badge could detect a radiation dose as little as 1 millirad, which is comparable to current commercial badges. Yeast also is known to be genetically similar to human tissue. Data from the badges can, therefore, inform future work on how radiation damage happens to human DNA and proteins. For yeast, radiation primarily affects the cell walls of the membrane and mitochondria.